1. Field of the Invention
The present invention relates to non-invasive measurement of internal information in a scattering medium by causing light having various incident angle components to be incident on the scattering medium, and detecting light diffused during propagation in the scattering medium. More particularly, this invention relates to a method for measuring internal information in a scattering medium and an apparatus for the same, which are capable of measuring absolute values of an absorption coefficient and a transport scattering coefficient of the scattering medium, absolute quantities of a specific absorptive constituent and a specific scattering constituent, a degree of oxygen saturation of hemoglobin, their time changes, their spatial distributions etc. and which are capable of improving measurement accuracy.
2. Related Background Art
Demands for precise measurement of an absorption coefficient, a scattering coefficient and a transport scattering coefficient in a scattering medium such as a living body, the concentration of a specific absorptive constituent, an absolute quantity of a specific absorptive constituent, their time changes, and their spacial distributions have been very strong. There are several attempts therefore to achieve this such as a method using continuous light, or modulated light (e.g., pulsed light, square wave light, sinusoidal wave modulated light etc.), and a method using lights having different wavelengths (e.g., dual wavelength spectroscopy). It has been known that the behavior of light diffused during propagation in the scattering medium can be analyzed, experimented and examined in accordance with Monte Carlo calculation using a computer, and can be described and analyzed with photon diffusion theory. Present conditions with regard to measurement of a scattering medium are described in detail, for example, in the following references 1)-6) (note that hereinafter, the references will be referred to with a reference number X) or a superscript .sup.X) in sentences).